FreeRDP up to 3.26.x H.264 Codec libfreerdp/codec/h264.c avc444_ensure_buffer heap-based overflow

Summaryinfo

A vulnerability was found in FreeRDP up to 3.26.x. It has been classified as critical. This issue affects the function avc444_ensure_buffer of the file libfreerdp/codec/h264.c of the component H.264 Codec. This manipulation causes heap-based overflow. This vulnerability is registered as CVE-2026-55191. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability classified as critical was found in FreeRDP up to 3.26.x. Affected by this vulnerability is the function avc444_ensure_buffer of the file libfreerdp/codec/h264.c of the component H.264 Codec. The manipulation with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

FreeRDP is a free implementation of the Remote Desktop Protocol. Prior to 3.27.0, FreeRDP clients that negotiate RDPGFX AVC444 with an H.264 decoder backend calculate the intermediate YUV444 allocation size in libfreerdp/codec/h264.c with 32-bit multiplication in avc444_ensure_buffer. A malicious RDP server can supply surface dimensions for which piDstStride multiplied by padDstHeight wraps to a small nonzero value, causing winpr_aligned_recalloc to allocate an undersized buffer before YUV420CombineToYUV444 writes using the actual stride and rectangle dimensions. This can cause a client crash and may permit code execution through attacker-influenced heap corruption. This issue is fixed in version 3.27.0.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-55191 since 06/16/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details are known, but no exploit is available.

Upgrading to version 3.27.0 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Remote Access Software

Name

• FreeRDP

Version

• 3.0
• 3.1
• 3.2
• 3.3
• 3.4
• 3.5
• 3.6
• 3.7
• 3.8
• 3.9
• 3.10
• 3.11
• 3.12
• 3.13
• 3.14
• 3.15
• 3.16
• 3.17
• 3.18
• 3.19
• 3.20
• 3.21
• 3.22
• 3.23
• 3.24
• 3.25
• 3.26

License

• open-source

Website

• Product: https://github.com/FreeRDP/FreeRDP/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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